148 FORMATION OF SHELLS OF ANIMALS, ETC., 
with their now solid contents, these edges become sharply 
serrated. Lastly, in and towards the centre of the lens, 
where the coalescence is complete, the dentate lines which 
indicate the lateral extent of the radiating fibres become 
obliterated, showing, at this part, a thorough incorporation 
of the material of which they are composed, and with this 
the process of molecular coalescence of the lens termi- 
nates. Mr. Nunneley, in a paper contaimed in the 
‘Quarterly Journal of Microscopical Science’ for April, 
1858, gives a plate of the epithelial cells from the posterior 
part of the capsule of the lens of a sheep, showing lines of 
cells, concerning which he observes that “ were it not that 
similar cells are found in Petit’s canal I should feel 
inclined to think that they are not merely the means of 
nutrition to the lens, but that they are lens-fibres in 
progress of development.’ This observation seems to me 
to show that Mr. Nunneley would have persisted in enter- 
taining his first impression as to the nature of these cor- 
puscles, which I have no doubt is the right one, had he not 
been diverted from this view by some preconceived physio- 
logical theory concerning the nutrition of the lens. The 
dentate lines, corresponding doubtless to the radiating lines 
of feeble attraction in the artificially formed calculi, are 
the last to become obliterated; and this does not take 
place until the predominant force is the attraction of 
tenacity. These lines are distinctly serrated only in the 
fish, bemg merely undulating and irregular im mammals. 
The circumstance of irregularity in these lines, as con- 
trasted with that of the artificial and some of the natural 
products, is probably to be accounted for by the difference 
of mechanical conditions under which in the two cases they 
areformed. These conditions in the former,—the artificial 
product—applying at the same time to the entire spherical 
